1. Technical Field
The present invention relates to a subscriber's extension telephone unit coupled by a radio link to an associated telephone line and more particularly to a subscriber's extension telephone unit having a completely self contained dipole antenna.
2. Background Art
To comply with current Federal Communication Commission Regulations, most wireless extension telephone units operate on a full duplex basis, transmitting incoming signals from the line via a base unit radio transmitter operating on a frequency of approximately 1.7 MHz. These signals are received at a portable or remote wireless extension unit while signals from the remote unit are transmitted back to the base unit for connection to the telephone line at a frequency of approximately 49 MHz.
Because under current Federal Communication Commission Regulations, only limited power can be utilized in the transmitters incorporated into wireless extension telephone units and certain restrictions also apply to the antennas utilized in this service, a number of different approaches have been utilized to provide efficient antennas and thus secure maximum range between the base and remote units incorporated in wireless extension telephone systems. Most commercially available wireless extension telephone remote units utilize telescoping type whip antennas as transmitting antennas. These units may extend to almost five feet in length, (approximately 1/4 wave length at 49 MHz) or be shortened by inclusion of a loading coil or take the form of a helix. Units of this type are shown in U.S. Pat. Nos. 3,366,745, 3,476,882 and 3,567,787 as well as a number of more recent patents.
Wireless telephone extension remote units equipped with such antennas bear strong resemblence physically to the so-called "Walky-Talky" or "Handy-Talky" units utilized for emergency communications, amateur service and so called "citizen band" usage. While these units have the advantage of portability, the necessity (to gain maximum efficiency) of raising or lowering the antenna and the danger of striking other individuals or objects and causing damage thereto is a prime concern. Furthermore, telescoping whip antennas traditionally used for this service are easily destroyed or damage due to inadvertent placement in locations where they may be sat upon or other objects placed upon them. Likewise, they are subject to bending and twisting.
One solution to the drawbacks of the aforementioned whip type antennas for remote wireless extension units is taught in the Rovette.TM. cordless telephone distributed by Fracom/Rovafone International. This unit provides a wireless extension telephone unit consisting of a separate base and hand set genrally similar to the "Princess".RTM. and "Starlite".RTM. telephones manufactured by Western Electric and GTE Automatic Electric respectively. In the Rovette telephone, the antenna is included in the handset cord extending between the telephone base and the handset. While this arrangement eliminates many of the objections found with the whip type antenna, requirements for two separate pieces as a portion of the remote telephone unit restricts its portability and usage and at the same time substantially adds to the cost of the telephone unit.
Cordless telephones use various switching arrangements to disable the transmitter to conserve battery energy when not in the two way communication mode. At least one cordless telephone disables the transmitter when the handset is placed on the base by a switch on the base unit, while other commercial units use a manual switch, or a switch actuated by extending a telescoping antenna.
Accordingly, it is the object of the present invention to provide a new and improved wireless extension telephone remote unit with a self contained dipole antenna which overcomes the shortcomings found in many previous wireless extension telephone remote units.